Dynamic anterior cervical plate system having moveable segments, instrumentation, and method for installation thereof

ABSTRACT

An anterior cervical plating system includes moveable plate segments to vary the overall length of the plate and allow and/or cause intersegmental compression of vertebral bodies. The plating system is capable of both passive and active dynamization and has the ability to produce the former from the latter.

RELATED APPLICATIONS

[0001] This application claims the benefit of provisional applicationNo. 60/379,589, filed May 9, 2002; and provisional application No.60/377,916, filed May 3, 2002; provisional application No. 60/356,318,filed Feb. 12, 2002; provisional application No. 60/355,194, filed Feb.8, 2002; provisional application No. 60/296,681, filed Jun. 6, 2001;provisional application No. 60/296,680, filed Jun. 6, 2001; provisionalapplication No. 60/296,060, filed Jun. 4, 2001; provisional applicationNo. 60/296,059, filed Jun. 4, 2001; all of which are incorporated byreference herein.

BACKGROUND

[0002] The use of plates, screws, and locks to prevent separation andbacking out of screws from the plate, for use on the anterior aspect ofthe cervical spine to provide alignment and stability as an adjunct tofusion of adjacent vertebral bodies is known in the art. Also known inthe art is that compressive load, within a physiological range across afusion site, is beneficial to the fusion process. Conversely, a failureto maintain a compressive load across a fusion site, or to have a gap inthe fusion construct continuity may lead to a failure to achieve fusioncalled pseudoarthrosis. A primary purpose of the aforementioned cervicalhardware is to provide stability during the healing and fusion process.The fusion process occurs in part through a process called “creepingsubstitution” by which new living bone replaces the dead bone such asthat of a bone graft. The fusion process involves a phase of boneresorption as preliminary to the formation of the new bone. It ispossible then for the bone resorption to result in gaps in thecontinuity of the fusion mass, such that if the hardware is sufficientlyrigid, such as occurs as a result of increasing the strength of thecomponents and constraining the relationship of the screws to the plate,those gaps may persist and increase in size as the hardware holds thebone portions separated rather than allowing those bone portions to movetogether to close those gaps. This holding apart of the bone portions(called distraction) can therefore lead to a failure of fusion(pseudoarthrosis). These rigid systems by a combination of not inducingcompression at the fusion site and of holding the bone portions to befused apart may cause a “distraction pseudoarthrosis.”

[0003] Alternative cervical plating systems have attempted to preventdistraction pseudoarthrosis by allowing the vertebral bodies to collapsetowards each other as needed during the fusion process. Generally thishas been done by allowing the bone screws to be free to move relative tothe plate, that is, movement such as sliding, swiveling, rotating, andangulating, independent of whether the screws are prevented fromseparating or backing out of the plates such as by the use of locks.Undesired multidirectional instability can occur in such plating systemsthat is counter to the very purpose of such hardware which is toincrease or provide for stability.

[0004] Another approach to solving this problem has been to attach byscrews a block to each of the vertebral bodies to be fused and then toallow those blocks to slide up and down on a pair of rods. Each of theseconstructs have in common that they sacrifice stability, the ability tohold the bones to be fused rigidly in place and prevent undesiredmotion; for the ability to allow, but not cause the vertebral bodies tocollapse.

[0005] There exists therefore a need for an improved anterior cervicalplating system that is: (1) sufficiently rigid to maintain the desiredalignment of the vertebral bodies to be fused; (2) capable of inducingcompressive load across the fusion site; and/or (3) capable of allowingfor the motion of the vertebral bodies towards each other to prevent orto close any gaps in the continuity of the fusion construct, while stillbeing capable of preventing motion in all other directions. When similarchallenges have been faced at other skeletal locations, the solutioninvolved anchoring the bone screws through the far cortex of the boneportions to be joined, in effect anchoring the screws in such a way asto make it possible for the screws to force movement of the plates. Inthe cervical spine anteriorly, however, it has been found to be highlyundesirable to drive the bone screws through the far cortex of thevertebral bodies, as this is where the spinal cord is located. Thereremains therefore a need for an improved cervical plating system as justdescribed that does not require that the bone screws penetrate the farcortex to achieve the desired purpose as described.

[0006] The size of the vertebral bodies and the spacing between thevertebral bodies varies from patient to patient. The height of thevertebral bodies and the discs therebetween may vary level by level evenin the same person. Thus, a plate of correct length does not necessarilyhave bone screw receiving holes correctly positioned to overlie thevertebral bodies in accordance with the spacing of the vertebral bodiesto which the plate is to be applied. As a result, conventional platingsystems of the past had to be manufactured in many different lengths andspacing configurations which were nevertheless fixed in an attempt toprovide plates for many, though still possibly not all, of the varioussizes and spacings of the vertebral bodies to which the plate was to beapplied. For example, in a multi-segment plate the length of the platewould need to correspond to the overall length of the vertebral bodiesto be joined and actual distances therebetween and the screw holes ofthe plate arranged to overlie the vertebral bodies. In order to coverthe possible range of sizes, health care facilities would need to carrya large inventory of different sizes of plates, in some cases as many assixty different sized plates would be needed. Such a large inventory isan expensive undertaking and still worse, facilities with a highcaseload need to invest in more than one of each plate size to providefor the possibility of overlapping demand for the same plate size.Facilities with lower caseloads may find it prohibitively expensive tostock an inventory of plates sufficient to cover the range of possiblesizes and thus might not be able to afford to stock a set at all or haveless than all sizes of plates needed for all cases. Manufactures cannotafford to place a set of plates on consignment in facilities with lowcaseloads as the number of sales would not cover the carrying costs ofthe plates.

[0007] There exists therefore a need for an improved anterior cervicalplating system that (1) allows for the overall adjustability of thelength of the plate; (2) allows for variations in spacing between thebone screw receiving holes of the plate portions corresponding to theattachment point of the plate to the vertebral bodies; (3) reduces therequisite plate inventory; and (4) can avoid or prevent distractionpseudoarthrosis without itself introducing multidirectional instability.

SUMMARY OF THE INVENTION

[0008] The present invention in one preferred embodiment is a dynamicanterior cervical plating system including a plate comprising segmentsin moveable relationship to each other adapted to allow for the overalladjustability of the length of the plate and for variations in theintersegmental spacing of the bone screw receiving holes, to createand/or store a compressive load across a disc space between two adjacentvertebral bodies to be fused, and/or to allow motion of the vertebralbodies toward each other to prevent or close gaps in the continuity of afusion construct, while preferably preventing motion in all otherdirections when in use. As used herein, a spinal fusion segment isdefined as two vertebral bodies with an intervertebral implant, made ofbone or an artificial material, in the disc space therebetween. As usedherein, a fusion construct is defined as a spinal fusion segment plusthe hardware, such as a plate and screws for example.

[0009] The present invention in another preferred embodiment is adynamic, modular, anterior cervical plating system including a platecomprising assembleable segments in moveable relationship to each otheradapted to allow for the overall adjustability of the length of theplate and for variations in the intersegmental spacing of the bone screwreceiving holes, to create and/or store a compressive load across a discspace between two adjacent vertebral bodies to be fused, and/or to allowmotion of the vertebral bodies toward each other to prevent or closegaps in the continuity of a fusion construct, while preferablypreventing motion in all other directions when in use.

[0010] The ability to permit the movement of adjacent vertebral bodiestoward one another is referred to herein as “dynamization.” Dynamizationmay be “passive” allowing the plate to shorten when a shortening force,such as a compressive load is applied. Dynamization may be “active”wherein the plating system stores energy to induce shortening of thefusion construct should the opportunity present. The present inventionplating system may passively dynamize, actively dynamize, provide acombination of both, as well as convert and store certain compressivestresses encountered during the healing phase as will be more fullydescribed herein.

[0011] The plate segments also can be moved to vary the spacing betweenthe plate segments as well as the overall length of the plate so thatthe size of the plate may be adjusted to correspond to a range of sizesand spacing of the adjacent vertebral bodies to which the plate is beingapplied; thereby greatly reducing the inventory of plate sizes needed.The moveable plate segments combine to form the plate. Each platesegment is attached to a vertebral body to be fused by at least one bonescrew and preferably a pair of bone screws, which when inserted, arepreferably prevented from backing out of the plate by at least onelocking element adapted to lock at least two bone screws to the plate.In an alternative embodiment, a locking element is adapted to lock asingle bone screw to the plate.

[0012] The paths of the bone screws through the plate may be fixed orvariable. If the paths are variable, they may be more or less stabledepending on how resistant to motion the screws are relative to theplate when the screws are locked to the plate. To the extent that screwsare sufficiently stable in relation to the plate to make use of thepresent inventive teaching, these screw, plate, and lock combinations orvariations thereon are also within the broad scope of the presentinvention.

[0013] In a preferred embodiment of the present invention, after each ofthe segments of the plate are attached to a respective one of thevertebral bodies to be fused, the plate is capable of movement from afirst or elongated position to a second or shorter position, a processgenerally referred to as “passive dynamization”—that is the ability ofthe system to allow the plated spinal segment to shorten in response tounmet compressive loads to allow for the bone portions to be fused tomove close together to restore contact. A preferred embodiment of thispresent invention is capable of allowing for this passive dynamizationwhile preventing undesirable motions along and around all axes otherthan the motion along the longitudinal axis of the plate.

[0014] In another preferred embodiment of the present invention, theplate segments are articulated in such a way that even the one freedomof movement that is along the longitudinal axis of the plate isselectively limited to the desired passive dynamization that isshortening of the plate construct. This preferred embodiment of thepresent invention will shorten as required to maintain loaded contact ofthe bone portions to be fused, and if challenged, resist any forces suchas those that would accompany cervical extension that would distract ordestabilize the construct by elongating it. A further benefit of thisembodiment is its ability to store and impart a compressive load acrossthe fusion site referred to herein as “active dynamization” whereinenergy stored in the system shortens the plate construct if conditionspermit. This load can be applied by the surgeon at the time of surgeryand/or be produced during the healing phase by harnessing thecompressive loads such as occur randomly with neck motion. Compressiveload within a physiological range has been shown to have a beneficialeffect on the healing of bone. The induction of a compressive loadacross vertebral bodies to be fused, induces bone growth and when boneresorption occurs at the interface of the graft or implant and thevertebral bodies to be joined, those vertebral bodies are urged to movecloser together, thus avoiding the formation of a gap therebetween andthereby acting to mitigate against pseudoarthrosis.

[0015] Alternatively, various embodiments of the present invention allowthe surgeon to induce a desired amount of preload (compressive force)across the fusion site and to permit a desired amount of shortening ofthe construct—“active dynamization” should the opportunity occur; andyet lock the system to prevent any further shortening as might present arisk of deformity or be otherwise undesirable. Such a system urges thebone portions closer together.

[0016] In a preferred embodiment, a pre-load force can be applied to theplate segments such that while the plate segments may undergo no addedmotion initially, there is a selective force applied to the platesegments and the plate segments are capable of motion in only onedirection, such that should resorption occur at one of the fusioninterfaces then the plate segments are not only free to move in adirection toward one another, and only in that direction, but are alsourged to do so to relieve that preload force. Such a system urges thevertebral bodies together over time as resorption permits.

[0017] Alternatively, in another embodiment of the plate of the presentinvention, a desired amount of preload (compressive force) may beinduced across the fusion site to permit active dynamization should theopportunity occur, without locking the system such that after activedynamization is exhausted (if exhausted), then the plate will stillallow passive dynamization to occur thereafter.

[0018] In another embodiment of the present invention, the plateincludes a structural feature such as a groove, recess, slot, cam, orpivot, within its physical perimeter to engage a tool to cooperativelymove segments of the plate towards each other. These embodiments of thepresent invention may be adapted to allow for passive, active, or activeplus passive dynamization, and when used to store compressive load toallow for or prevent further motion thereafter. In a preferred versionof this embodiment, the structural feature contained within the platefor generating the compressive load and/or shortening the plate, mayalso serve as the locking mechanism to limit the amount of furthershortening possible.

[0019] Various embodiments of the plating system of the presentinvention provide one or more of the following advantages:

[0020] 1. The requisite plate inventory is reduced as each plate maycover a range of sizes. The plate of the present invention includesmultiple segments which may be of varying sizes wherein the segments areadapted to be assembled so as to be adjustable to provide for the sizeand spacing apart of the vertebral bodies to which the plate is to beapplied. The plate may have its segments moved relative to one anotherso that the spacing between the plate segments may be adjusted so as tocorrespond to the actual distances between the vertebral bodies to befused in a multi-segment construct for a more precise fit. The height ofthe discs and the vertebral bodies may vary level by level even in thesame person. Thus, the ability to adjust the distances between thesegments of the plates that correspond to the attachments to thosevertebral bodies allows for a more precise fit of the plate to the spinewith a reduced inventory of the number of plates required to do so.

[0021] 2. It is possible to precisely contour each segment separately.

[0022] 3. The plating system of the present invention reduces the riskthat the plate construct will be discovered to be too short or too longafter the attachment process has commenced.

[0023] 4. It is possible to compress and dynamize levels selectively.

[0024] 5. The fasteners that link the segments can be tightened to lockthe segments after they are compressed or, alternatively, can allow forfurther motion of the plate segments together.

[0025] 6. The same hardware can provide for passive dynamization or berigidly fixed depending on the fasteners used to link plate segments.

[0026] 7. The system can allow for passive dynamization, activedynamization, the combination of passive and active dynamization, or canconvert body motion into active dynamization.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1A is an exploded top perspective view of a plate, afastener, and a locking element in accordance with a preferredembodiment of the present invention.

[0028]FIG. 1B is an exploded top perspective view of a plate, afastener, and a locking element in accordance with another preferredembodiment of the present invention.

[0029]FIG. 1C is an exploded top perspective view of a plate, afastener, and locking elements in accordance with another preferredembodiment of the present invention.

[0030]FIG. 1D is an exploded top perspective view of a plate, afastener, and locking elements in accordance with another preferredembodiment of the present invention.

[0031]FIG. 2A is an exploded bottom perspective view of the plate,fastener, and locking element of FIG. 1A.

[0032]FIG. 2B is an exploded bottom perspective view of the plate,fastener, and locking element of FIG. 1B.

[0033]FIG. 2C is an exploded bottom perspective view of the plate,fastener, and locking elements of FIG. 1C.

[0034]FIG. 2D is an exploded bottom perspective view of the plate,fastener, and locking elements of FIG. 1D.

[0035]FIG. 3A is a top plan view of the plate, fastener, and lockingelement of FIGS. 1A and 1B.

[0036]FIG. 3C is a top plan view of the plate, fastener, and lockingelements of FIGS. 1C and 1D.

[0037]FIG. 4A is a bottom plan view of the plate, fastener, and lockingelement of FIG. 1A.

[0038]FIG. 4B is a bottom plan view of the plate, fastener, and lockingelement of FIG. 1B.

[0039]FIG. 4C is a bottom plan view of the plate, fastener, and lockingelements of FIG. 1C.

[0040]FIG. 4D is a bottom plan view of the plate, fastener, and lockingelements of FIG. 1D.

[0041]FIG. 5A is an end view of the plates of FIGS. 1A-1D.

[0042]FIG. 6A is a side elevation view of the plates of FIGS. 1A and 1B.

[0043]FIG. 6C is a side elevation view of the plates of FIGS. 1C and 1D.

[0044]FIG. 7A is a partial cross sectional view of the plates of FIGS.1A and 1C.

[0045]FIG. 7B is a partial cross sectional view of the plates of FIGS.1B and 1D.

[0046]FIG. 8A is an enlarged fragmentary view of the plates of FIGS. 1Aand 1C and an alternative embodiment of a fastener in accordance withthe present invention.

[0047]FIG. 8B is an enlarged fragmentary view of the plates of FIGS. 1Band 1D and an alternative embodiment of a fastener in accordance withthe present invention.

[0048]FIG. 9A is an enlarged fragmentary cross sectional view of anembodiment of the ratchetings in the upper and lower portions of theplates of FIGS. 1A-1D in a first position.

[0049]FIG. 10A is a fragmentary cross sectional view of FIG. 9A in asecond position.

[0050]FIG. 11A is an enlarged fragmentary cross sectional view of apreferred embodiment of the ratchetings in the upper and lower portionsof the plates of the present invention in a first position.

[0051]FIG. 12A is a fragmentary cross sectional view of FIG. 11A in asecond position.

[0052]FIG. 13A is a top perspective view of the plates and fasteners ofFIGS. 1A and 1B and instrumentation for compressing the plates andinstrumentation for locking the fasteners in accordance with a preferredembodiment of the present invention.

[0053]FIG. 13C is a top perspective view of the plates and fasteners ofFIGS. 1C and 1D and instrumentation for compressing the plates andinstrumentation for locking the fasteners in accordance with a preferredembodiment of the present invention.

[0054]FIG. 14A is a top plan view of the plates and fasteners of FIGS.1A and 1B in a compressed state with the instrumentation of FIG. 13Ashown in cross section engaging the ends of the plate to compress theplate in the direction of the arrows and with the instrumentationengaging the fastener.

[0055]FIG. 14C is a top plan view of the plates and fasteners of FIGS.1C and 1D in a compressed state with the instrumentation of FIG. 13Cshown in cross section engaging the ends of the plate to compress theplate in the direction of the arrows and with the instrumentationengaging the fastener.

[0056]FIG. 15A is a partial cross sectional view along line 15A-15A ofFIG. 14A for the plate of FIG. 1A.

[0057]FIG. 15B is a partial cross sectional view along line 15A-15A ofFIG. 14A for the plate of FIG. 1B.

[0058]FIG. 15C is a partial cross sectional view along line 15C-15C ofFIG. 14C for the plate of FIG. 1C.

[0059]FIG. 15D is a partial cross sectional view along line 15C-15C ofFIG. 14C for the plate of FIG. 1D.

[0060]FIG. 16A is a top perspective view of a plate, a fastener, andlocking element in accordance with another preferred embodiment of thepresent invention.

[0061]FIG. 16C is a top perspective view of a plate, a fastener, andlocking elements in accordance with another preferred embodiment of thepresent invention.

[0062]FIG. 17A is a top plan view of the plate and fastener of FIG. 16A.

[0063]FIG. 17C is a top plan view of the plate, fastener, and lockingelements of FIG. 16C.

[0064]FIG. 18A is a top plan view of the plate of FIG. 16A in anelongated state with fastener.

[0065]FIG. 18C is a top plan view of the plate of FIG. 16C in anelongated state, fastener, and locking elements.

[0066]FIG. 19A is a bottom plan view of the plate and fastener of FIG.16A.

[0067]FIG. 19B is a bottom plan view of another preferred embodiment ofthe plate and fastener of FIG. 16A.

[0068]FIG. 19C is a bottom plan view of the plate and fastener of FIG.16C.

[0069]FIG. 19D is a bottom plan view of another preferred embodiment ofthe plate and fastener of FIG. 16C.

[0070]FIG. 20A is a partial cross sectional view along line 20A-20A ofthe plate of FIG. 17A.

[0071]FIG. 20B is a partial cross sectional view along line 20A-20A ofFIG. 17A of a plate and fastener in accordance with another preferredembodiment of the present invention.

[0072]FIG. 21A is an exploded top perspective view of the plate,fastener, and locking element of FIG. 16A.

[0073]FIG. 21B is an exploded top perspective view of the plate,fastener, and locking element of FIG. 16A in accordance with anotherpreferred embodiment of the present invention.

[0074]FIG. 21C is an exploded top perspective view of the plate,fastener, and locking elements of FIG. 16C.

[0075]FIG. 21D is an exploded top perspective view of the plate,fastener, and locking elements of FIG. 16C in accordance with anotherpreferred embodiment of the present invention.

[0076]FIG. 22A is an exploded bottom perspective view of the plate,fastener, and locking element of FIG. 16A.

[0077]FIG. 22B is an exploded bottom perspective view of the plate,fastener, and locking element of FIG. 21B.

[0078]FIG. 22C is an exploded bottom perspective view of the plate,fastener, and locking elements of FIG. 16C.

[0079]FIG. 22D is an exploded bottom perspective view of the plate,fastener, and locking elements of FIG. 21D.

[0080]FIG. 23A is a top plan view of the plate and fastener of FIG. 16Aand a partial fragmentary perspective view of an instrument forcompressing the plate and securing the fastener in accordance withanother preferred embodiment of the present invention.

[0081]FIG. 23C is a top plan view of the plate, fastener, and lockingelements of FIG. 16C and a partial fragmentary perspective view of aninstrument for compressing the plate and securing the fastener inaccordance with another preferred embodiment of the present invention.

[0082]FIG. 24A is an enlarged cross sectional view of the plate of FIG.16A with the instrument of FIG. 23A engaging the fastener and positionedwithin the plate.

[0083]FIG. 24B is an enlarged cross sectional view of another preferredembodiment of the plate of FIG. 16A with the instrument of FIG. 23Aengaging the fastener and positioned within the plate.

[0084]FIG. 24C is an enlarged cross sectional view of the plate of FIG.16C with the instrument of FIG. 23C engaging the fastener and positionedwithin the plate.

[0085]FIG. 24D is an enlarged cross sectional view of another preferredembodiment of the plate of FIG. 16C with the instrument of FIG. 23Cengaging the fastener and positioned within the plate.

[0086]FIG. 25A is a fragmentary top plan view of one of the plates ofFIGS. 16A and 16C in an elongated state with the instrument of FIGS. 23Aand 23C shown in cross section engaging the fastener and positionedwithin the plate.

[0087]FIG. 26A is a fragmentary top plan view of one of the plates ofFIGS. 16A and 16C in a compressed state with the instrument of FIGS. 23Aand 23C shown in cross section engaging the fastener and positionedwithin the plate to rotate the fastener in the direction of the arrow tocompress the plate.

[0088]FIG. 27A is an exploded top perspective view of a plate, afastener, and locking element in accordance with another preferredembodiment of the present invention.

[0089]FIG. 27B is an exploded top perspective view of a plate, afastener, and locking element in accordance with another preferredembodiment of the present invention.

[0090]FIG. 27C is an exploded top perspective view of a plate, afastener, and locking elements in accordance with another preferredembodiment of the present invention.

[0091]FIG. 27D is an exploded top perspective view of a plate, afastener, and locking elements in accordance with another preferredembodiment of the present invention.

[0092]FIG. 28A is a cross sectional view transverse to the longitudinalaxis of the plate of FIGS. 27A-27D.

[0093]FIG. 29A is a top plan view of a plate, fasteners, and lockingelement in accordance with another preferred embodiment of the presentinvention.

[0094]FIG. 29C is a top plan view of a plate, fasteners, and lockingelements in accordance with another preferred embodiment of the presentinvention.

[0095]FIG. 30A is an exploded top perspective view of the plate,fasteners, and locking element of FIG. 29A.

[0096]FIG. 30B is an exploded top perspective view of another preferredembodiment of the plate, fasteners, and locking element of FIG. 29A.

[0097]FIG. 30C is an exploded top perspective view of the plate,fasteners, and locking elements of FIG. 29C.

[0098]FIG. 30D is an exploded top perspective view of another preferredembodiment of the plate, fasteners, and locking elements of FIG. 29C.

[0099]FIG. 31A is an exploded bottom perspective view of the plate,fasteners, and locking element of FIG. 30A.

[0100]FIG. 31B is an exploded bottom perspective view of the plate,fasteners, and locking element of FIG. 30B.

[0101]FIG. 31C is an exploded bottom perspective view of the plate,fasteners, and locking elements of FIG. 30C.

[0102]FIG. 31D is an exploded bottom perspective view of the plate,fasteners, and locking elements of FIG. 30D.

[0103]FIG. 32A is a top plan view of the plates, fasteners, and lockingelement of FIGS. 30A and 30B.

[0104]FIG. 32C is a top plan view of the plates, fasteners, and lockingelements of FIGS. 30C and 30D.

[0105]FIG. 33A is a bottom plan view of the plate and fasteners of FIG.30A.

[0106]FIG. 33B is a bottom plan view of the plate and fasteners of FIG.30B.

[0107]FIG. 33C is a bottom plan view of the plate, fasteners, andlocking elements of FIG. 30C.

[0108]FIG. 33D is a bottom plan view of the plate, fasteners, andlocking elements of FIG. 30D.

[0109]FIG. 34A is a side elevation view of the plates of FIGS. 30A and30B.

[0110]FIG. 34C is a side elevation view of the plates of FIGS. 30C and30D.

[0111]FIG. 35A is a partial cross sectional view along the longitudinalaxis of the plate of FIG. 30A.

[0112]FIG. 35B is a partial cross sectional view along the longitudinalaxis of the plate of FIG. 30B.

[0113]FIG. 35C is a partial cross sectional view along the longitudinalaxis of the plate of FIG. 30C.

[0114]FIG. 35D is a partial cross sectional view along the longitudinalaxis of the plate of FIG. 30D.

[0115]FIG. 36A is a top plan view of the plates in an elongatedposition, fasteners, and locking element of FIGS. 30A and 30B.

[0116]FIG. 36C is a top plan view of the plates in an elongatedposition, fasteners, and locking elements of FIGS. 30C and 30D.

[0117]FIG. 37A is a top perspective view of one of the plates of FIGS.30A and 30B and another preferred embodiment of instrumentation forcompressing the plate and instrumentation for locking the fastener inaccordance with the present invention.

[0118]FIG. 37C is a top perspective view of one of the plates of FIGS.30C and 30D and another preferred embodiment of instrumentation forcompressing the plate and instrumentation for locking the fastener inaccordance with the present invention.

[0119]FIG. 38A is a top plan view of one of the plates of FIGS. 30A and30B in a compressed state with the instrumentation of FIG. 37A shown incross section engaging the ends of the plate to compress the plate inthe direction of the arrows, an alternative embodiment ofinstrumentation for engaging an intermediary portion of the plate tocompress the plate in the direction of the arrows in dotted line, andinstrumentation engaging the fastener and positioned within the plate.

[0120]FIG. 38C is a top plan view of one of the plates of FIGS. 30C and30D in a compressed state with the instrumentation of FIG. 37C shown incross section engaging the ends of the plate to compress the plate inthe direction of the arrows, an alternative embodiment ofinstrumentation for engaging an intermediary portion of the plate tocompress the plate in the direction of the arrows in dotted line, andinstrumentation engaging the fastener and positioned within the plate.

[0121]FIG. 39A is a side elevation view of the plate of FIG. 38A withthe instrumentation shown in partial fragmentary, hidden line, and crosssectional views.

[0122]FIG. 39C is a side elevation view of the plate of FIG. 38C withthe instrumentation shown in partial fragmentary, hidden line, and crosssectional views.

[0123]FIG. 40A is an exploded top perspective view of a plate,fasteners, and a locking element in accordance with another preferredembodiment of the present invention.

[0124]FIG. 40B is an exploded top perspective view of a plate,fasteners, and a locking element in accordance with another preferredembodiment of the present invention.

[0125]FIG. 40C is an exploded top perspective view of a plate,fasteners, and locking elements in accordance with another preferredembodiment of the present invention.

[0126]FIG. 40D is an exploded top perspective view of a plate,fasteners, and locking elements in accordance with another preferredembodiment of the present invention.

[0127]FIG. 41 is a top plan view of a plate, fasteners, and lockingelements in accordance with another preferred embodiment of the presentinvention.

[0128]FIG. 42 is an exploded top plan view of a plate, fasteners, andlocking elements in accordance with another preferred embodiment of thepresent invention.

[0129]FIG. 43 is an enlarged fragmentary cross sectional view of theplate, locking element, and bone screws of FIG. 42.

[0130]FIG. 44 is an enlarged fragmentary cross sectional view of aplate, locking element, and bone screws in accordance with anotherembodiment of the present invention.

[0131]FIG. 45 is a fragmentary top plan view of another preferredembodiment of a plate and a locking element adapted to lock at least twobone screws and a fastener in accordance with the present invention.

[0132]FIG. 46 is a fragmentary top plan view of another preferredembodiment of a plate and a locking element adapted to lock at least twobone screws and a fastener in accordance with the present invention.

[0133]FIG. 47a is an enlarged fragmentary cross sectional view of alocking element and bone screw in accordance with a preferred embodimentof the present invention.

[0134]FIG. 47b is an enlarged fragmentary cross sectional view of alocking element and bone screw in accordance with another preferredembodiment of the present invention.

[0135]FIG. 47c is an enlarged fragmentary cross sectional view of alocking element and bone screw in accordance with yet another embodimentof the present invention.

[0136]FIG. 47d is an enlarged fragmentary cross sectional view of thelocking element and bone screw of FIG. 47c in an angled position.

[0137]FIG. 47e is an enlarged fragmentary cross sectional view of aself-locking bone screw in accordance with a further embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0138] Reference will now be made in detail to the present preferredembodiments (exemplary embodiments) of the invention, examples of whichare illustrated in the accompanying drawings. Wherever possible, thesame reference numbers will be used throughout the drawings to refer tothe same or like parts.

[0139] The present invention is for use in the cervical spine wheredynamization is highly desired to prevent distraction pseudoarthrosisand to maintain a compressive load across the fusion interfaces. Thepresent invention in one preferred embodiment is directed to a cervicalplate generally having at least two movable segments that are attachedto the vertebral bodies to be fused and connected in such a way as topermit dynamization of the vertebral bodies preferably along thelongitudinal axis of the plate. The movement of the segments relative toone another may be accompanied by a reduction in the overall length ofthe plate.

[0140] Where possible, the reference numerals in the figures arefollowed by a letter “a”, “b”, “c”, or “d” corresponding to preferredembodiments of the present invention, respectively. For example, adescription of a feature identified by a reference numeral followed bythe reference letter “a” and also applicable to a feature identified bya reference numeral followed by a letter “b”, “c”, or “d” will not berepeated for each of the corresponding reference numerals.

[0141]FIGS. 1A, 2A, 3A, 4A, 5A, 6A and 7A show a preferred embodiment ofa cervical plate 100 a in accordance with the present invention. Plate100 a is preferably formed of a first segment 102 a and a second segment104 a in moveable relationship to one another. First and second segments102 a, 104 a can be of various lengths and/or configurations such thatwhen the segments are assembled preferably overlapping at least in part,plates of various lengths and/or configurations can be formed to cover arange of sizes. First and second segments 102 a, 104 a can be of thesame or different lengths and can be coupled to each other or to anintermediate segment as shown in FIGS. 29A, 30A, 31A, 32A, 33A, 34A,35A, 36A, 37A, 38A, 39A, and -40A and described below in connection withother preferred embodiments of the present invention. The overall lengthof plate 100 a and the spacing of segments 102 a, 104 a can be adjustedby moving segments 102 a, 104 a relative to one another.

[0142] In this preferred embodiment of the present invention, adetachable fastener 106 a couples together first and second segments 102a, 104 a. Fastener 106 a is configured to be detachably attached to atleast one of first and second segments 102 a, 104 a, to permit theassembly of two or more plate segments. Fastener 106 a is detachable topermit for the assembly of the plate segments by the surgeon and allowsfor the complete uncoupling of first and second segments 102 a, 104 afrom one another. As used herein, “detachable fastener” is defined as afastener that can be assembled by the surgeon at the time of use andonce attached is meant to still be removable and then reattachable bythe surgeon. As shown in FIG. 7A, fastener 106 a, for example, may beembodied in the form of a screw having a head 108 a, a shaft 112 a, anda thread 116 a.

[0143] As shown in FIG. 8A, in another preferred embodiment fastener 106a′ may be configured to be tightened to only one of first and secondplate segments 102 a, 104 a so as to permit movement of first and secondsegments 102 a, 104 a relative to one another when fastener 106 a′ isfully tightened. For example, fastener 106 a′ may have a shoulder 110 aadapted to bear upon second segment 104 a as indicated by arrow C.Shoulder 110 a is dimensioned so as to create a gap 111 a between head108 a′ and first segment 102 a so as to still permit a specific anddesired motion of first and second segments 102 a, 104 a relative to oneanother when fastener 106 a′ is fully tightened. The limited motion offirst and second segments 102 a, 104 a relative to one another providesfor dynamization of the spinal segment to be fused in that thosevertebral bodies are allowed to move closer together to maintaincontact.

[0144] As shown in FIGS. 1A and 2A, first segment 102 a preferably hasan upper surface 118 a, a lower surface 120 a, a medial portion 122 a,and an end 124 a. First segment 102 a preferably includes bone screwreceiving holes 126 a proximate end 124 a. Bone screw receiving hole 126a is preferably configured to receive a single bone screw or the bonescrew receiving holes also may be configured to receive more than onebone screw. By way of example only and not limitation, a bone screwreceiving hole may be in the form of a slot sized to receive at leasttwo bone screws.

[0145] Preferably, at least two of bone screw receiving holes 126 a maybe oriented in plate 100 a to overlie the anterior aspect of a singlecervical vertebral body adjacent a disc space to be fused, though theinvention is not so limited. For example, a first pair of bone screwreceiving holes 126 a may be configured to overlie the anterior aspectof a first cervical vertebral body adjacent a disc space to be fused andat least a second pair of bone screw receiving holes 126 a may beoriented in plate 100 a to overlie the anterior aspect of a secondcervical vertebral body adjacent the disc space to be fused.

[0146] Bone screw receiving hole 126 a may, though need not be,configured to form an interference fit with at least a portion of thetrailing end of a properly dimensioned bone screw to be receivedtherein. Bone screw receiving holes 126 a may be configured, for exampleonly, so that at least one of bone screw receiving holes 126 a may holda bone screw in a fixed relationship to the plate or may hold a bonescrew in a moveable relationship, such as a variable angularrelationship, described below. By way of example only and notlimitation, bone screw receiving hole 126 a may have a reduced dimensionproximate lower surface 120 a of segment 102 a to form a seat 127 a.Seat 127 a may have a surface adapted to contact at least a portion of abone screw inserted therein. The surface may be at least in part planar,at least in part curved, or have any other configuration suitable forcontacting at least a portion of a bone screw.

[0147] End 124 a of first segment 102 a may also include a toolengagement area 128 a adapted to cooperatively engage instrumentationfor holding plate 100 a and instrumentation for moving first and secondsegments relative to one another to induce a desired amount ofcompressive force across the fusion sites and to permit a desired amountof shortening of plate 100 a. Medial portion 122 a preferably has afastener receiving opening 130 a adapted to accommodate fastener 106 ato couple first and second segments 102 a, 104 a to one another.

[0148] Fastener receiving opening 130 a is preferably configured topermit selected movement of fastener 106 a therein and to permitselected motion of first and second segments 102 a, 104 a along thelongitudinal axis of plate 100 a. Fastener receiving opening 130 a mayinclude a shoulder 132 a recessed from upper surface 118 a of firstsegment 102 a adapted to contact the underside of head 108 a of fastener106 a in the tightened position to prevent movement of first and secondsegments 102 a, 104 a relative to one another. Alternatively, if afastener 106 a′ is used, shoulder 110 a contacts second segment 104 aand the underside of head 108 a′ is positioned relative to shoulder 132a to permit movement of first and second segments 102 a, 104 a relativeto each other along the longitudinal axis of the plate when in thetightened position providing for dynamization of the vertebral bodies tobe fused to occur, if needed. Fastener 106 a and fastener receivingopening 130 a cooperate to prevent complete uncoupling of first andsecond segments 102 a, 104 a from one another when fastener 106 a isinstalled. For example, fastener receiving opening 130 a may beconfigured to prevent head 108 a of fastener 106 a from passingtherethrough.

[0149] Lower surface 120 a of first segment 102 a includes a tabreceiving recess 134 a for receiving a tab 136 a described below.

[0150] Second segment 104 a has an upper surface 138 a, a lower surface140 a, a medial portion 142 a, and an end 144 a. Second segment 104 apreferably has bone screw receiving holes 126 a proximate end 144 a. End144 a may also include a tool engagement area 146 a adapted tocooperatively engage instrumentation for holding plate 100 a andinstrumentation for moving first and second segments 102 a, 104 arelative to one another to induce a desired amount of compressive forceacross the fusion site and to permit a desired amount of shortening ofplate 100 a. Medial portion 142 a preferably includes a fastenerreceiving opening 148 a for receiving a portion of fastener 106 a. Asfirst and second segments of plate 100 a are modular and assembleable,fastener receiving opening 148 a is configured to permit detachableattachment of fastener 106 a.

[0151] Fastener receiving opening 148 a preferably has a thread 150 aadapted to engage with thread 116 a of fastener 106 a. The threadedengagement of fastener 106 a to fastener receiving opening 148 a permitsfirst segment 102 a and second segment 104 a to be attached to eachother when fastener 106 a is sufficiently rotated and tightened. Asfastener 106 a is rotated further, first and second segments 102 a, 104a are secured together and locked and do not move relative to eachother. Alternatively, if fastener 106 a′ shown in FIG. 8A is used in thetightened position, first and second segments 102 a, 104 a are capableof moving relative to each other.

[0152] Lower surfaces 120 a, 140 a of first and second segments 102 a,104 a are preferably at least in part concave along at least a portionof the longitudinal axis of the plate, may be biconcave at least inpart, that is, concave along the longitudinal axis of plate 100 a andconcave transverse to the longitudinal axis of the plate, or may haveany shape suitable for the intended purpose transverse to thelongitudinal axis of the plate. A person skilled in the art willappreciate that plate 100 a may be adapted for other curvatures or haveno curvature without departing from the intended purpose within thebroad scope of the present invention. Lower surfaces 120 a, 140 a arepreferably adapted to contact at least a portion of the vertebral bodiesto be fused and may be configured to conform to the anterior aspect ofat least a portion of the vertebral bodies.

[0153] Second segment 104 a preferably includes a tab 136 a extendingfrom medial portion 142 a. Tab 136 a is configured to cooperativelyengage a tab receiving recess 134 a in the lower surface 120 a of firstsegment 102 a. Tab 136 a acts as a spring to maintain first and secondsegments 102 a, 104 a aligned along the longitudinal axis of plate 100a. Tab 136 a also functions to limit movement of first segment 102 a ina direction transverse to longitudinal axis of plate 100 a to preventend 124 a from dropping down beyond a desired position. This limitedmovement of first segment 100 a prevents medial portion 122 a of firstsegment 102 a from lifting away from medial portion 142 a beyond adesired position, so that ratchetings 150 a are not overly separated andrendered less effective as described in more detail below. It isappreciated that other configurations of segments 102 a, 104 a arepossible to hold apart segments 102 a, 104 a and to limit movement ofthe segments in a direction transverse to the longitudinal axis of theplate. For example, the longitudinal curvatures of first and secondsegments 102 a, 104 a can be slightly different to spring apart segments102 a, 104 a. For example, the radius of curvature of the lower surfaceof segment 102 a may be different than the radius of curvature of theupper surface of segment 104 a.

[0154] At least a portion of lower surface 120 a of first segment 102 aand upper surface 138 a of second segment 104 a are preferablyconfigured to interdigitate with one another to permit selectedadjustment of the length of plate 100 a. For example, lower surface 120a and upper surface 138 a may include a surface configuration, such asratchetings 152 a, configured to cooperatively interdigitate to permitselected and sequential movement along the longitudinal axis of plate100 a. The ratchetings are preferably biased to allow movement in onepreferred direction along the longitudinal axis of the plate so as toallow shortening of the plate and resist lengthening of the plate.

[0155]FIGS. 9A and 10A show an embodiment of ratchetings having aconfiguration that is useful if no movement of first and second segments102 a, 104 a is desired after fastener 106 a is tightened. A preferredangular relationship of the cross section of ratchetings 152 a ₁ is a45-45-90 degree triangular relationship. As shown in FIG. 9A, in a firstposition, the peaks and valleys of ratchetings 152 a ₁ are cooperativelymating. Ratchetings 152 a ₁ permit for the fixed positioning of firstand second segments 102 a, 104 a relative to one another to create aselected length of plate 100 a. As shown in FIG. 10A, the peaks andvalleys are separated to permit movement of the first and secondsegments in the directions of the arrows along the longitudinal axis ofplate 100 a. In order for first and second segments 102 a, 104 a to moverelative to one another, there must be sufficient freedom of movementfor the segments to move apart in order to clear the height of the peaksof ratchetings 152 a ₁. Accordingly, in a preferred embodiment fastener106 a is configured to have at least one position that permits movementof the first and second segments along the longitudinal axis of plate100 a as well as along an axis transverse to the longitudinal axis ofplate 100 a such that ratchetings 152 a can move apart. Fastener 106 acan be tightened to a second position to resist or prevent movement ofsegments 102 a, 104 a relative to one another. For example, movement ofsegments 102 a, 104 a can be resisted in a direction along at least aportion of the longitudinal axis of plate 100 a.

[0156]FIGS. 11A and 12A show another preferred embodiment of ratchetings152 a ₂ having a forward-facing configuration for permitting movement ina single direction. The configuration of ratchetings 152 a ₂ is usefulwhen movement of first and second segments 102 a, 104 a is desired topermit further shortening of the plate. A preferred angular relationshipof the triangular cross section of ratchetings 152 a ₂ is a 30-60-90degree triangular relationship. As shown in FIG. 12A, due to the forwardfacing angle of ratchetings 152 a ₂, sliding movement of first andsecond segments 102 a, 104 a in the direction, as indicated by thearrow, along the longitudinal axis of plate 100 a is facilitated by theramped surface 154 a. In contrast, sliding movement in the oppositedirection is restricted by vertical wall 156 a. Movement of segments 102a, 104 a is limited to a single direction with ratchetings 152 a ₁ andby limiting the separation of segments 102 a, 104 a along an axistransverse to the longitudinal axis of plate 100 a with fastener 106 aor 106 a′.

[0157] In a preferred embodiment, fastener 106 a or 106 a′ is configuredto have at least one position that permits movement of first and secondsegments 102 a, 104 a in both directions along the longitudinal axis ofplate 100 a as well as along an axis transverse to the longitudinal axisof plate 100 a such that ratchetings 152 a ₂ can move apart. Forexample, in a first position fastener 106 a can be less than fullytightened to plate 100 a as desired by the surgeon to permit movement offirst and second segments relative to each other. Fastener 106 a′ canfurther have a second position that permits movement of segments 102 a,104 a relative to one another only in a single direction along thelongitudinal axis of plate 100 a and limits movement along an axistransverse to the longitudinal axis of plate 100 a. Therefore, plate 100a can be shortened if the distance between the two adjacent vertebralbodies decreases, even after plate 100 a is installed, so that thevertebral bodies are not held apart by plate 100 a, to prevent theoccurrence of pseudoarthrosis. One of the benefits of a forward-facingconfiguration of ratchetings 152 a ₂ is the ability to store and imparta compressive load across the fusion site. The compressive load storedmay be applied by the surgeon and/or compressive loads that occurrandomly with neck motion during the healing phase. First and secondsegments 102 a, 104 a may be pre-adjusted to correspond to theappropriate size and spacing of the adjacent vertebral bodies to befused prior to placement of plate 100 a against the vertebral bodies bymoving first and second segments 102 a, 104 a relative to one anotherwhile fastener 106 a is only partially tightened for the purpose ofappropriately adjusting the length of the plate. Then, fastener 106 amay be further tightened to secure first and second segments 102 a, 104a in the desired position.

[0158] Plates 100 a and 100 b preferably include at least one bone screwlock adapted to lock to the plate only a single bone screw inserted intoone of the bone screw receiving holes. The plates of the presentinvention may include more than one bone screw lock, each lock beingadapted to lock to the plate only a single bone screw inserted into oneof the bone screw receiving holes. Preferably, the bone screw lockphysically blocks the bone screw from unwanted loosening or unwantedbacking out from the plate.

[0159]FIGS. 47a-47 d show preferred embodiments of locking elements forlocking bone screws in accordance with the present invention. Forexample, the bone screw locks may be in the form of a screw, a rivet, acap, or a cover. It is appreciated that any locking element for lockinga single one of the bone screws known to one of ordinary skill in theart would be within the scope of the present invention.

[0160]FIG. 47a shows an enlarged fragmentary cross sectional view of alocking element 172 a ₁ and a bone screw 174 a ₁. Locking element 172 a₁ threadably engages bone screw receiving hole 126 a to prevent bonescrew 174 a ₁ from backing out. In this embodiment, locking element 172a ₁ locks bone screw 174 a ₁ in a fixed relationship to plate 100 a.

[0161]FIG. 47b is an enlarged fragmentary cross sectional view of alocking element 172 a ₂ and a bone screw 174 a ₂. Locking element 172 a₂ threadably engages bone screw receiving hole 126 a to prevent bonescrew 174 a ₂ from backing out. In this embodiment, locking element 172a ₂ is adapted to hold bone screw 174 a ₂ in an angular relationship toplate 100 a. Examples of preferred fixed-angled single locking elementsare taught by Michelson in U.S. Pat. No. 6,139,550, (the '550 patent)entitled “Skeletal Plating System,” the disclosure of which is herebyincorporated by reference herein. Locking element 172 a ₂ may alsopermit movement of bone screw 174 a ₂ relative to plate 100 a.

[0162]FIGS. 47c and 47 d are enlarged fragmentary cross sectional viewsof a locking element 172 a ₃ and bone screw 174 a ₃ in accordance withanother embodiment of the present invention. Locking element 172 a ₃threadably engages bone screw receiving hole 126 a to prevent bone screw174 a ₃ from backing out. In this embodiment, locking element 172 a ₃ isadapted to hold bone screw 174 a ₃ in an angular relationship to plate100 a. Locking element 172 a ₃ may also permit movement of bone screw174 a ₃ relative to plate 100. Locking element 172 a ₃ is adapted toadjustably lock bone screw 174 a ₃ in a variable angle relationshiprelative to plate 100 a. Bone screw 174 a ₃ preferably has a roundedhead 176 a ₃ that cooperates with the bottom surface of single lockingelement 172 a ₃, thus allowing screw 174 a ₃ to move relative to plate100 a. Examples of preferred variable-angled single locking elements aretaught by Michelson in the '550 patent the disclosure of which is herebyincorporated by reference herein.

[0163]FIG. 47e is an enlarged fragmentary cross sectional view of aself-locking bone screw 174 a ₄ in accordance with another embodiment ofthe present invention. Bone screw 174 a ₄ has thread 178 a ₄ adapted tothreadably engage bone screw receiving hole 126 a. The thread pattern ofthread 178 a ₄ is has a tighter pitch than the thread pattern of thebone engaging thread of bone screw 174 a ₄. The different thread pitchesprevent bone screw 174 a ₄ from backing out after installation iscompleted.

[0164] It is appreciated that various types of bone screws and singlelock systems may be utilized with the plates of the present invention.

[0165] With appropriate embodiments of the plates described herein, thesurgeon may induce a desired amount of “preload,” or compressive forceacross the fusion site after plate attachment by moving first and secondsegments 102 a, 104 a toward one another to shorten the length of plate100 as desired. Inducing a preload enhances fusion by maintaining acompressive force between adjacent vertebral bodies and reducing thechance that gaps might develop as new living bone replaces the dead boneduring the fusion process.

[0166]FIGS. 13A, 14A, and 15A show a preferred embodiment ofinstrumentation 200 a for compressing and locking plate 100 a.Instrumentation 200 a has a handle 202 a with a pair of tongs 204 a, 206a in moveable relationship to each. Tongs 204 a, 206 a are configured tocooperatively engage ends 124 a, 144 a of first and second segments, 102a, 104 a, respectively. Instrumentation 200 a may be used to hold andposition plate 100 a in a desired position at the fusion site during atleast a portion of the procedure for installing plate 100 a. Anyinstrument capable of engaging the plate so as to serve the intendedpurpose would be within the scope of the instrumentation and method ofthe present invention. As an example only, methods and instrumentationfor installing plates to the cervical spine, including a pilot holeforming punch to create bone screw receiving holes in the vertebralbodies coaxially aligned with the bone screw receiving holes with theplate, are taught and described by Michelson in the '721 patent,incorporated by reference herein. After segments 102 a, 104 a have beenattached to the adjacent vertebral bodies with an appropriate fasteningelement, such as bone screws, instrument 200 a can be used to movesegments 102 a, 104 a toward one another to shorten the length of plate100 a and create a compressive load across the disc space. After thedesired length of plate 100 a is achieved, an instrument 208 a having ahead 210 a configured to cooperatively engage fastener 106 a is used totighten fastener 106 a to secure first and second segments 102 a, 104 ain a desired position. When in a secured position, segments 102 a, 104 amay maintain a compressive load across the disc space if desired. Head210 a of instrument 208 a may have a hex-shaped configuration.

[0167]FIGS. 1B, 2B, 4B, 7B, 8B, and 15B show another preferredembodiment of a cervical plate 100 b in accordance with the presentinvention. In this preferred embodiment of the present invention, plate100 b may include at least one bone screw lock adapted to lock to theplate only a single bone screw inserted into one of bone screw receivingholes 126 b such as described above in relation to plate 100 a and anon-detachable fastener 106 b configured to couple together first andsecond segments 102 b, 104 b. Fastener 106 b is configured to benon-detachably attached to at least one of first and second segments 102b, 104 b to couple together two or more plate segments. Fastener 106 bis non-detachable to prevent non-destructive complete uncoupling offirst and second segments 102 b, 104 b from one another during normaluse. As used herein, “non-detachable fastener” is defined as a fastenerthat once attached is not meant to be removed and then reattached. Asshown in FIG. 7B, fastener 106 b, for example, may be embodied in theform of a rivet having a head 108 b, 0 a shaft 112 b, and a base 114 b.By way of example only and not limitation, base 114 b may be coupled tosecond segment 104 b so that it is permanently attached, but is stillcapable of an element of rotation about its longitudinal axis. Shaft 112b of fastener 106 b preferably has a thread 116 b.

[0168] Fastener receiving opening 148 b of plate 100 b is configured topermit non-detachable attachment of fastener 106 b while permitting anelement of rotation of fastener 106 b about its longitudinal axis. Forexample as shown in FIG. 2B, the bottom portion of fastener receivingopening 148 b proximate lower surface 140 b of second segment 104 b mayhave a smaller dimension than the maximum dimension of base 114 b (e.g.flared portion of a rivet) of fastener 106 b so as to prevent passage ofthe end portion therethrough. Moreover, the bottom portion of fastenerreceiving opening 148 b may be beveled to accommodate base 114 b (e.g.flared portion) of fastener 106 b so that it is generally flush orrecessed to the bottom surface and preferably does not impede closecontact of lower surface 140 b with the surface of the vertebral bodies.The first and second plate segments may be modular components of variousconfigurations assembled by the manufacturer of the plate and providedto the surgeon in an assembled state. In the assembled state, the platehas a non-detachable fastener that prevents non-destructive completeuncoupling of the first and second segments during normal use.

[0169]FIGS. 1C, 2C, 3C, 4C, 6C, 13C, 14C, and 15C show another preferredembodiment of a cervical plate 100 c in accordance with the presentinvention. In this preferred embodiment of the present invention, plate100 c may include a detachable fastener configured to couple togetherfirst and second segments 102 c, 104 c such as described above inrelation to plate 100 a and a bone screw lock adapted to lock at leasttwo bone screws inserted in bone screw receiving holes 126 c. Bone screwlocks 172 c are coupled to plate 100 c and may be removable or may benon-detachably attached to plate 100 c. Bone screw locks 172 c may becoupled to plate 100 c prior to the insertion of the bone screws intobone screw receiving holes 126 c. Alternatively, the bone screw locksmay be coupled to the plate after the insertion of the bone screws intothe bone screw receiving holes.

[0170] As shown in FIGS. 1C, 2C, 3C,4C, 14C, and 15C, by way of exampleonly and not limitation, bone screw lock 172 c may have a toolengagement portion 174 c adapted to cooperatively engage an instrumentused for coupling bone screw lock 172 c to plate 100 c and at least onecutout 176 c. Each cutout 176 c is oriented so as to permit introductionof a bone screw into an adjacent bone screw receiving hole when bonescrew lock 172 c is coupled to plate 100 c and in the appropriateorientation. It is appreciated that other configurations of the bonescrew lock are possible so as to permit introduction of a bone screwinto a bone screw receiving hole adjacent to the bone screw lock withoutinterference from the bone screw lock.

[0171] Plate 100 c may have an opening 178 c for receiving at least aportion of locking element 172 c and may, but need not, include a recess180 c for receiving at least a portion of locking element 172 c therein.Bone screw lock 172 c may have a stem 182 c configured to fit at leastin part within opening 178 c in plate 100 c. Stem 182 c and opening 178c may be threaded to threadably engage bone screw lock 172 c to plate100 c. Alternatively, at least a portion of the interior perimeter ofrecess 180 c and at least a portion of the perimeter of the bone screwlock may be threaded to threadably engage the bone screw lock to theplate.

[0172] In a preferred embodiment, bone screw locks 172 c are configuredto move from an initial position, that permits the insertion of bonescrews into the bone screw receiving holes, to a final position that isadapted to extend over at least a portion of at least two of the bonescrews to retain the bone screws to the plate. The bone screw lock maybe adapted to be rotated from the initial position to the finalposition, and preferably, less than a full rotation of the bone screwlock rotates the bone screw lock from the initial position to the finalposition. In a preferred embodiment, the bone screw lock in the finalposition covers at least a portion of at least two of the bone screwreceiving holes.

[0173] In another preferred embodiment, at least a portion of the bonescrew lock slides from the initial position to the final position. Thebone screw lock can slide over at least a portion of at least two of thebone screw receiving holes and/or slide over at least a portion of atleast two bone screws in the bone screw receiving holes. The bone screwlock may be in the form of a screw, a rivet, a cap, a cover, or have anyother configuration suitable for its intended purpose. The bone screwlock may have a head that is at least in part circular.

[0174] Where it is desired to lock more than one bone screw to the platewith one bone screw lock, any lock suitable for locking a plurality ofbone screws to an anterior cervical plate known to those of ordinaryskill in the art may be utilized, including but not limited to, the bonescrew locks taught by Michelson in U.S. Pat. No. 6,193,721 (the '721patent), incorporated by reference herein.

[0175]FIGS. 1D, 2D, 4D, and 15D show another preferred embodiment of acervical plate 100 d in accordance with the present invention. In thispreferred embodiment of the present invention, plate 100 d may include anon-detachable fastener configured to couple together first and secondsegments 102 d, 104 d such as described above in relation to plate 100 band a bone screw lock adapted to lock at least two bone screws insertedinto bone screw receiving holes 126 d such as described above inrelation to plate 100 c.

[0176]FIGS. 16A, 17A, 18A, 19A, 20A, 21A, and 22A show another preferredembodiment of a cervical plate 300 a having an internal compressionmechanism in accordance with the present invention. Plate 300 a issimilar to plate 100 a except that fastener receiving opening 330 a andfastener 306 a function as part of a mechanism to move first and secondsegments 302 a, 304 a relative to one another to change the length ofplate 300 a to generate a compressive load across the disc space betweentwo adjacent vertebral bodies to be fused. Fastener receiving opening330 a includes instrument pin receiving recesses 362 a ₁ and 362 a ₂ forcooperating with the pin of an instrument 400 a (described below) formoving first and second segments 302 a, 304 a relative to one another.In addition, instead of a tab 136 a, plate 300 a has pins 358 a andtracks 360 a to maintain first and second segments 302 a, 304 a alignedalong the longitudinal axis of plate 300 a. Bone screw lock 372 a isadapted to lock to plate 300 a at least two bone screws inserted in bonescrew receiving holes 326 a.

[0177] As shown in FIGS. 20A, 21A, and 22A, first segment 302 apreferably has two pins 358 a depending therefrom for engagement incorresponding tracks 360 a in second segment 304 a. Pins 358 a slideablyengage tracks 360 a, respectively, and travel therein when first andsecond segments 302 a, 304 a are moved relative to one another. Tracks360 a are staggered along the length of medial portion 342 a and pins358 a are staggered along the length of medial portion 322 a to maintainfirst and second segments 302 a, 304 a aligned along the longitudinalaxis of plate 300 a. It is appreciated that any plate configuration toachieve the intended purpose of maintaining first and second segments302 a, 304 a aligned along the longitudinal axis of the plate would bewithin the scope of the present invention.

[0178]FIGS. 23A, 24A, 25A, and- 26A show a preferred embodiment ofinstrumentation 400 a used for compressing and locking plate 300 a.Instrumentation 400 a has a working end 402 a configured tocooperatively engage fastener receiving opening 330 a and fastener 306a. After segments 302 a, 304 a have been attached to the adjacentvertebral bodies with an appropriate fastening element, such as bonescrews, instrument 400 a can be used to move segments 302 a, 304 atoward one another to shorten the length of plate 300 a, create acompressive load across the disc space, and concurrently tightenfastener 306 a (if desired) to secure first and second segments 302 a,304 a in a preferred position. Working end 402 a of instrument 400 apreferably has a driver portion 404 a configured to cooperatively engagedriver receiving opening 364 a in fastener 306 a. Driver portion 404 ais preferably hex-shaped. Working end 402 a preferably has a pin 406 aextending therefrom and displaced from driver portion 404 a to engageone of pin receiving recesses 362 a ₁ and 362 a ₂, respectively, whendriver portion 404 a is engaged with driver receiving opening 364 a infastener 306 a. With driver portion 404 a engaging fastener 306 a andpin 406 a inserted in pin receiving recess 362 a ₂ as shown in FIG. 25A,instrument 400 a rotates fastener 306 a in the direction of arrow A asshown in FIG. 26A to move first segment 302 a toward second segment 304a in the direction of arrow B to reduce the length of plate 300 a andcan if desired concurrently tighten fastener 306 a. The configuration ofplate 300 a provides for an internal compression mechanism that can beoperated by a driver instrument eliminating the need for an externallyapplied compression apparatus for shortening plate 300 a and creating acompressive load.

[0179]FIGS. 19B, 20B, 21B, 22B, and 24B show another preferredembodiment of a cervical plate 300 b in accordance with the presentinvention similar to plate 300 a. In this preferred embodiment of thepresent invention, plate 300 b may include at least one bone screw lockadapted to lock to the plate only a single bone screw inserted into oneof bone screw receiving holes 326 b such as described above in relationto plate 100 a and a non-detachable fastener 306 b configured to coupletogether first and second segments 302 b, 304 b such as described abovein relation to plate 100 b.

[0180]FIGS. 16C, 17C18C, 19C, 21C, 22C, 23C, and 24C show anotherpreferred embodiment of a cervical plate 300 c in accordance with thepresent invention similar to plate 300 a. In this preferred embodimentof the present invention, plate 300 c may include a detachable fastenerconfigured to couple together first and second segments 302 c, 304 csuch as described above in relation to plate 100 a and a bone screw lockadapted to lock at least two bone screws inserted in bone screwreceiving holes 326 c such as described above in relation to plate 100c.

[0181]FIGS. 19D, 21D, 22D, and 24D show another preferred embodiment ofa cervical plate 300 d in accordance with the present invention similarto plate 300 a. In this preferred embodiment of the present invention,plate 300 d may include a non-detachable fastener configured to coupletogether first and second segments 302 d, 304 d such as described abovein relation to plate 100 b and a bone screw lock adapted to lock atleast two bone screws inserted into bone screw receiving holes 326 dsuch as described above in relation to plate 100 c.

[0182]FIGS. 27A and 28A show another preferred embodiment of a cervicalplate 500 a in accordance with the present invention. Plate 500 a issimilar to plate 100 a except that first segment 502 a is configured toreceive at least a portion of second segment 504 a therein in a tongueand groove configuration. As shown in FIG. 28A, first segment 502 apreferably has a C-shaped cross section and second segment 504 apreferably has a T-shaped cross section. The configurations of segments502 a, 504 a in this embodiment of the present invention keep segments502 a, 504 a aligned along the longitudinal axis of plate 500 a andlimit movement of segments 502 a, 504 a in a direction generallytransverse to the longitudinal axis of plate 500 a. A person of ordinaryskill in the art would appreciate that other configurations ofcooperatively engaging first and second segments 502 a, 504 a arepossible without departing from the intended purpose within the broadscope of the present invention. Bone screw lock 572 a is adapted to lockto plate 500 a one bone screw inserted in one of bone screw receivingholes 526 a.

[0183]FIG. 27B shows another preferred embodiment of a cervical plate500 b in accordance with the present invention similar to plate 500 a.In this preferred embodiment of the present invention, plate 500 b mayinclude at least one bone screw lock adapted to lock to the plate only asingle bone screw inserted into one of bone screw receiving holes 526 bsuch as described above in relation to plate 100 a and a non-detachablefastener 506 b configured to couple together first and second segments502 b, 504 b such as described above in relation to plate 100 b.

[0184]FIG. 27C shows another preferred embodiment of a cervical plate500 c in accordance with the present invention similar to plate 500 a.In this preferred embodiment of the present invention, plate 500 c mayinclude a detachable fastener configured to couple together first andsecond segments 502 c, 504 c such as described above in relation toplate 100 a and a bone screw lock adapted to lock at least two bonescrews inserted in bone screw receiving holes 526 c such as describedabove in relation to plate 100 c.

[0185]FIG. 27D shows another preferred embodiment of a cervical plate500 d in accordance with the present invention similar to plate 500 a.In this preferred embodiment of the present invention, plate 500 d mayinclude a non-detachable fastener configured to couple together firstand second segments 502 d, 504 d such as described above in relation toplate 100 b and a bone screw lock adapted to lock at least two bonescrews inserted into bone screw receiving holes 526 d such as describedabove in relation to plate 100 c.

[0186]FIGS. 29A, 30A, 31A, 32A, 33A, 34A, 35A, and -36A show anotherpreferred embodiment of a cervical plate 600 a in accordance with thepresent invention. Plate 600 a is similar to plate 100 a except that itis configured for use across two levels of the cervical spine. Inaddition to the elements of plate 100 a, plate 600 a further includes anintermediate third segment 666 a between first and second segments 602a, 604 a. Third segment 666 a has a first end 668 a configured tocooperatively engage first segment 602 a. Third segment 666 a has asecond end 670 a configured to cooperatively engage second segment 604a. Third segment 666 a and first and second segments 602 a, 604 a arearticulated and can be moved to vary the spacing between the bone screwreceiving holes of the plate segments as well as the overall length ofthe plate. Third segment 666 a can be made of different lengths and/orconfigurations to vary the distance between first and second segments602 a, 604 a to further vary the spacing between the bone screwreceiving holes and further vary the overall length of the plate.

[0187] In a preferred embodiment of the present invention, plate 600 acould be provided to the health care facility in a set of segments. Forexample, a set or group of six segments could include a longer and ashorter one of first, second, and third segments 602 a, 604 a, 666 a.These segments could be assembled to cover a range of sizes. Additionalintermediate segments 666 a can be used to assemble a plate that coversadditional levels of the spine and preferably the spacing between platesegments would be adjustable.

[0188] First end 668 a of third segment 666 a has similar features tosecond segment 604 a including a fastener receiving recess 648 a, bonescrew receiving holes 626 a, ratchetings 652 a on at least a portion ofits upper surface 638 a, and a tab 636 a. Second end 670 a of thirdsegment 666 a has similar features to first segment 602 a including aratchetings 652 a on at least a portion of its lower surface 620 a and atab receiving recess 634 a. A first fastener 606 a couples togetherfirst segment 602 a to first end 668 a of third segment 666 a. A secondfastener couples together second segment 604 a to second end 670 a ofthird segment 666 a. Additional segments 666 a may be added for useacross more than two levels of the spine. Segments 666 a are configuredto be coupled together with first end 668 a of one segment 666 a tosecond end 670 a of another segment 666 a. Bone screw lock 672 a isadapted to lock to plate 600 a at least two bone screws inserted in bonescrew receiving holes 626 a.

[0189]FIGS. 37A, 38A, and- 39A show a preferred embodiment ofinstrumentation 700 a for compressing and locking plate 600 a.Instrumentation 700 a has a handle 702 a with a pair of tongs 704 a, 706a in moveable relationship to each. Tongs 704 a, 706 a are configured tocooperatively engage ends 624 a, 644 a of first and second segments, 602a, 604 a, respectively, to shorten the overall length of the plate andto apply a desired compressive load across multiple levels of the spine.Instrumentation 700 a may be used to position plate 600 a in a desiredposition at the fusion site during at least a portion of the procedurefor installing plate 600 a. An instrument may be used for holding theplate such as the instrumentation disclosed in the '721 patentincorporated by reference above. Instrument 700 a can be used to movesegments 602 a, 604 a toward one another and toward third segment 666 ato shorten the length of plate 600 a and create a compressive loadacross the respective disc spaces.

[0190] As shown in FIG. 38A, an alternative embodiment of instrument 700a′ may be used to move first or second segment 602 a, 604 a toward thirdsegment 666 a so that a compressive load may be applied to one discspace at a time. Instrument 700 a′ has a tong 704 a′ similar to tong 704a for engaging one of ends 624 a, 644 a of first and second segments 602a, 604 a, and forked tong 707 a for engaging the third segment as shownin FIG. 38A.

[0191] After the desired length of plate 600 a is achieved, aninstrument 708 a having a head 710 a configured to cooperatively engagefastener 606 a is used to tighten fastener 606 a to secure first,second, and third segments 602 a, 604 a, 666 a in a desired position.

[0192]FIGS. 30B, 31B, 33B, and 35B show another preferred embodiment ofa cervical plate 600 b in accordance with the present invention similarto plate 600 a. In this preferred embodiment of the present invention,plate 600 b may include at least one bone screw lock adapted to lock tothe plate only a single bone screw inserted into one of bone screwreceiving holes 626 b such as described above in relation to plate 100 aand a non-detachable fastener 606 b configured to couple together firstand second segments 602 b, 604 b such as described above in relation toplate 100 b.

[0193]FIGS. 29C, 30C, 31C, 32C, 33C, 34C, 35C, 36C, 37C, 38C, and 39Cshow another preferred embodiment of a cervical plate 600 c inaccordance with the present invention similar to plate 600 a. In thispreferred embodiment of the present invention, plate 600 c may include adetachable fastener configured to couple together first and secondsegments 602 c, 604 c such as described above in relation to plate 100 aand a bone screw lock adapted to lock at least two bone screws insertedin bone screw receiving holes 626 c such as described above in relationto plate 100 c.

[0194]FIGS. 30D, 31D, 33D, and 35D show another preferred embodiment ofa cervical plate 600 d in accordance with the present invention similarto plate 600 a. In this preferred embodiment of the present invention,plate 600 d may include a non-detachable fastener configured to coupletogether first and second segments 602 d, 604 d such as described abovein relation to plate 100 b and a bone screw lock adapted to lock atleast two bone screws inserted into bone screw receiving holes 626 dsuch as described above in relation to plate 100 c.

[0195]FIG. 40A shows another preferred embodiment of a cervical plate800 a in accordance with the present invention. Plate 800 a is similarto plate 600 a except that first segment 802 a is configured to receiveat least a portion of the first end 868 a of third segment 866 a thereinin a tongue and groove configuration and second end 870 a of thirdsegment 866 a is configured to receive at least a portion of secondsegment 804 a therein, in a tongue and groove configuration. A person ofordinary skill in the art would appreciate that other configurations ofcooperatively engaging first and second segments 802 a, 804 a arepossible without departing from the intended purpose within the broadscope of the present invention. Bone screw lock 872 a is adapted to lockto plate 800 a at least two bone screws inserted in bone screw receivingholes 826 a.

[0196]FIG. 40B shows another preferred embodiment of a cervical plate800 b in accordance with the present invention similar to plate 800 a.In this preferred embodiment of the present invention, plate 800 b mayinclude at least one bone screw lock adapted to lock to the plate only asingle bone screw inserted into one of bone screw receiving holes 826 bsuch as described above in relation to plate 100 a and a non-detachablefastener 806 b configured to couple together first and second segments802 b, 804 b such as described above in relation to plate 100 b.

[0197]FIG. 40C shows another preferred embodiment of a cervical plate800 c in accordance with the present invention similar to plate 800 a.In this preferred embodiment of the present invention, plate 800 c mayinclude a detachable fastener configured to couple together first andsecond segments 802 c, 804 c such as described above in relation toplate 100 a and a bone screw lock adapted to lock at least two bonescrews inserted in bone screw receiving holes 826 c such as describedabove in relation to plate 100 c.

[0198]FIG. 40D shows another preferred embodiment of a cervical plate800 d in accordance with the present invention similar to plate 800 a.In this preferred embodiment of the present invention, plate 800 d mayinclude a non-detachable fastener configured to couple together firstand second segments 802 d, 804 d such as described above in relation toplate 100 b and a bone screw lock adapted to lock at least two bonescrews inserted into bone screw receiving holes 826 d such as describedabove in relation to plate 100 c.

[0199]FIG. 41 shows a cervical plate 900 c with locking elements 902 cin accordance with another preferred embodiment of the presentinvention. Locking elements 902 c are adapted to lock at least two bonescrews installed in each of bone screw receiving holes 916 c,respectively. Locking element 902 c is in moveable relationship to plate900 c so that locking element 902 c can be pre-installed to plate 900 cprior to the insertion of bone screws into bone screw receiving holes916 c. During installation of the bone screws, locking element 902 c canbe slid to one side of the plate as shown in the top portion of theplate in FIG. 41 to allow for insertion of a first bone screw into afirst bone screw receiving hole 916 c on the opposite side of plate 900c. Locking element 902 c is then moved to the opposite side of plate 900c to permit insertion of a second bone screw into the second bone screwreceiving hole 916 c. Locking element 902 c is then moved to cover atleast a portion of both first and second bone screws and can be lockedin place by a screw 917 c as shown in the middle and bottom portions ofplate 900 c in FIG. 41.

[0200]FIGS. 42 and 43 show a cervical plate 1000 c with locking elements1002 c in accordance with another preferred embodiment of the presentinvention. Locking elements 1002 c are installed to cover at least aportion of two bone screw receiving holes 1016 c. In this embodiment,the bone screws are installed in bone screw receiving holes 1016 c andlocking element 1002 c is placed over at least a portion of two bonescrews to lock the bone screws. Locking element 1002 c can be held inplace with a screw 1017 c that passes at least in part through opening1003 c in locking element 1002 c and engages opening 1005 c in plate1000 c to lock two bone screws 1048 c to plate 1000 c as shown in FIG.43. Bone screws 1048 c preferably have a leading end configured forinsertion into the cervical spine and a head 1049 c opposite the leadingend that may be configured to contact locking element 1002 c. By way ofexample only, bone screws 1048 c may be configured to be in a fixedrelationship to plate 1000 c such as shown in FIG. 43.

[0201]FIG. 44 is a fragmentary cross sectional view of another preferredembodiment of a locking element 1002 c′ and bone screws 1048 c′. Lockingelement 1002 c′ has a bottom surface adapted to cooperate with a roundedportion of head 1049 c′ of bone screws 1048 c′ and is adapted to holdbone screws 1048 c′ in an angular relationship to plate 1000 c′.Examples of preferred fixed-angled locking elements are taught byMichelson the '550 patent hereby incorporated by reference herein.Locking element 1002 c′ may also permit movement of bone screw 1048 c′relative to plate 1000 c′. Locking element 1002 c′ may also be adaptedto adjustably lock bone screws 1048 c′ in a variable angle relationshiprelative to plate 1000 c′. Examples of preferred variable-angled lockingelements are taught by Michelson in the '550 patent. The rounded portionof head 1049 c′ permits bone screws 1048 c′ to be in a moveablerelationship, such as for example in a variable angular relationship toplate 1000 c′. Other configurations are possible for the intendedpurpose and are within the broad scope of the present invention.

[0202] Various methods for using and installing the plates of thepresent invention are disclosed in the '550 and '721 patents toMichelson identified above, incorporated by reference herein.

[0203]FIG. 45 shows a plate 1100 c and a locking element 1180 c adaptedto lock at least two bone screws and a fastener 1134 c in accordancewith the present invention. Preferably, locking element 1180 c isconfigured to be preinstalled to plate 1100 c prior to insertion of thebone screws in bone screw receiving holes 1116 c and attachment offastener 1134 c to plate 1100 c. Locking element 1180 c has a firstposition that permits insertion of bone screws in respective bone screwreceiving holes 1116 c and installation and/or movement of fastener 1134c. Locking element 1180 c has a second position that covers at least aportion of at least two bone screw receiving holes 1116 c and fastener1134 c to lock at least two bone screws and fastener 1134 c to plate1100 c. Locking element 1180 c may preferably be configured to rotatablyand/or slideably cover at least a portion of two bone screws in bonescrew receiving holes 1116 c and at least a portion of fastener 1134 c.

[0204]FIG. 46 shows another preferred embodiment of a plate 1200 c andlocking element 1280 c adapted to lock at least two bone screws and afastener 1234 c in accordance with the present invention. Lockingelement 1280 c is configured to be installed to plate 1200 c afterinsertion of bone screws in bone screw receiving holes 1216 c andattachment of fastener 1234 c to plate 1200 c. Locking element 1280 c isconfigured to cover at least a portion of at least two bone screwreceiving holes 1216 c and fastener 1234 c to lock at least two bonescrews and at least a portion of fastener 1234 c to plate 1200 c.Locking element 1280 c is preferably attached to plate 1200 c by a screw1217 c or by any other means suitable for the intended purpose.

[0205] The plates of present invention may include a bone screw systemthat allows the vertebrae to move toward an interposed bone graft, andeach other if necessary, instead of keeping the vertebrae apart duringthe occurrence of the resorption phase of the creeping substitutionprocess. For example, the '550 patent discloses three types ofscrew-plate-lock systems, which are themselves combinable with oneanother, as follows: (1) Passive Dynamic; (2) Self-Compressing; and (3)Active Dynamic and are incorporated by reference herein.

[0206] It is appreciated that for any of the embodiments of the platesdescribed herein can be made of, treated, coated, combined with,comprised of, or used with any source of osteogenesis, fusion promotingsubstances, bone growth promoting materials, bone, bone derivedsubstances or products, demineralized bone matrix, mineralizingproteins, ossifying proteins, bone morphogenetic proteins,hydroxyapatite, genes coding for the production of bone, substancesother than bone, and bone including, but not limited to, cortical bone.The plates, screws, fasteners, and/or screw locks may also be combinedwith material and/or substance for inhibiting scar formation. Theplates, screws, fasteners, and/or screw locks may be combined with anantimicrobial material and/or surface treated or coated to beantibacterial and/or antimicrobial, such as for example, by a silvercoating. At least a portion of the bottom surface of the plates canpreferably have a porous, and/or textured and/or roughened surface andmay be coated with, impregnated with, or comprise of fusion promotingsubstances (such as bone morphogenetic proteins) so as to encourage thegrowth of bone along the underside of the plate from bone portion tobone portion. The textured bottom surface also provides a medium forretaining fusion promoting substances with which the bottom surfacelayer can be impregnated prior to installation. The bottom surface ofthe plate may be given the desired porous textured form by roughblasting or any other conventional technology, such as etching, plasmaspraying, sintering, and casting for example. If porous so as to promotebone ingrowth, the bottom surface is formed to have a porosity or poresize in the order of 50-500 microns, and preferably 100-300 microns.Bone growth promoting substances with which the porous, textured bottomsurface can be impregnated include, but are not limited to, bonemorphogenetic proteins, hydroxyapatite, or hydroxyapatite tricalciumphosphate. The plate, screws, fasteners, and/or bone screw locks mayinclude at least in part a resorbable and/or bioresorbable materialwhich can further be impregnated with a bone growth material so that asthe resorbable and/or bioresorbable material is resorbed by the body ofthe patient, the bone growth material is released, thus acting as a timerelease mechanism. The bioresorbable material may be, for example, atleast in part bone. The plate of the present invention may be used incombination with a spinal fixation implant such as any object,regardless of material, that can be inserted into any portion of thespine, such as but not limited to interbody spinal implants, interbodyspinal fusion implants, structural bone grafts, mesh, cages, spacers,staples, bone screws, plates, rods, tethers of synthetic cords or wires,or other spinal fixation hardware. The interbody spinal fusion implantsmay be at least in part bone, for example only, an allograft interbodybone graft. Alternatively, the spinal interbody spinal fusion implantmay be at least in part artificial. At least one of the plate, screws,fasteners, and/or bone screw locks may be, if so desired, electrifiedfor purposes of stimulating bone growth and contributing to bone fusion.

[0207] Other embodiments of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. It is intended that the specificationand examples be considered as exemplary only, with a true scope andspirit of the invention being indicated by the following claims.

What is claimed is:
 1. A plate adapted to be applied to the anteriorhuman cervical spine for contacting the anterior aspects of at least twocervical vertebral bodies to be fused together, said plate comprising:at least a first plate segment adapted to be attached to one of theadjacent vertebral bodies to be fused and at least a second platesegment adapted to be attached to another one of the adjacent vertebralbodies to be fused, said at least first and second plate segmentsadapted to be connected to one another and at least in part overlappedto form said plate, said at least first and second plate segments beingin a moveable relationship to one another along a longitudinal axis ofsaid plate, each of said at least first and second plate segmentsincluding: a lower surface adapted to contact at least one of thecervical vertebral bodies and an upper surface opposite said lowersurface, said lower surface being concave at least in part along atleast a portion of the longitudinal axis of said plate; at least onebone screw receiving hole extending from said upper surface through saidlower surface, each of said bone screw receiving holes adapted tooverlie one of the cervical vertebral bodies and being adapted toreceive at least one bone screw for engaging the cervical vertebral bodyto attach said plate to the cervical spine; said first and second platesegments being configured to couple together in cooperative relationshipso as to facilitate movement of said first and second plate segments ina direction toward one another along the longitudinal axis of said plateand to resist movement of said first and said second plate segments in adirection away from one another along the longitudinal axis of saidplate.
 2. The plate of claim 1, wherein said first and second platesegments are configured to move in only a single direction toward oneanother along the longitudinal axis of said plate.
 3. The plate of claim1, wherein said first and second plate segments are configured to limitmovement of said first and second plate segments relative to one anotheralong the longitudinal axis of said plate.
 4. The plate of claim 1,wherein said first and second plate segments are configured so as to beable to completely restrict movement of said first and second platesegments relative to one another along at least a mid-longitudinal axisof said plate.
 5. The plate of claim 1, wherein said first and secondplate segments are configured so as to limit separation of said firstand second plate segments relative to one another when coupled together.6. The plate of claim 1, wherein at least one of said first and secondplate segments is configured to receive at least a portion of anotherone of said first and second plate segments therein.
 7. The plate ofclaim 6, wherein at least one of said first and second plate segmentshas a projection and at least one of said first and second platesegments has a groove configured to receive at least a portion of saidprojection.
 8. The plate of claim 1, wherein said first and second platesegments when attached to the adjacent vertebral bodies, respectively,are adapted to move toward one another in response to movement of theadjacent cervical vertebral bodies toward each other.
 9. The plate ofclaim 1, wherein said first and second plate segments when attached tothe adjacent vertebral bodies, respectively, are adapted to move theadjacent cervical vertebral bodies toward each other in response tomovement of said first and second plate segments moving toward eachother.
 10. The plate of claim 1, wherein said first and second platesegments when attached to the adjacent vertebral bodies, respectively,are adapted to maintain a compressive load across a disc space betweenthe adjacent cervical vertebral bodies.
 11. The plate of claim 1,wherein at least a portion of said upper surface of said second platesegment is convex at least in part along at least a portion of thelongitudinal axis of said plate
 12. The plate of claim 11, wherein saidconcave lower surface of said first plate segment has a radius ofcurvature that is different than the radius of curvature of said convexupper surface of said second plate segment.
 13. The plate of claim 1,wherein said at least first and second plate segments are configured tocooperate so as to maintain said first and second plate segmentsgenerally aligned along the longitudinal axis of said plate.
 14. Theplate of claim 1, wherein said at least first and second plate segmentsare configured to cooperate so as to limit movement of said first andsecond plate segments in a direction generally transverse to thelongitudinal axis of said plate.
 15. The plate of claim 1, wherein atleast a portion of said lower surface of said first plate segment isconfigured to cooperatively engage at least a portion of said uppersurface of said second plate segment.
 16. The plate of claim 1, whereinsaid at least a portion of said lower surface of said first platesegment is configured to interdigitate with at least a portion of saidupper surface of said second plate segment.
 17. The plate of claim 16,wherein said at least a portion of said lower surface of said firstplate segment and said at least a portion of said upper surface of saidsecond plate segment include ratchetings.
 18. The plate of claim 17,wherein said ratchetings are configured to permit movement of said firstand second plate segments toward one another in a first direction alonga mid-longitudinal axis of said plate and to restrict movement in adirection opposite to said first direction.
 19. The plate of claim 1,wherein at least one of said first and second plate segments is selectedfrom a group of plate segments of various lengths.
 20. The plate ofclaim 1, wherein at least one of said first and second plate segments isselected from a group of plate segments of various configurations. 21.The plate of claim 1, further comprising at least a third plate segmentadapted to be connected to at least one of said first and second platesegments to form said plate.
 22. The plate of claim 21, wherein saidthird plate segment is an intermediate plate segment configured to becoupled between at least two plate segments.
 23. The plate of claim 21,wherein at least one of said first, second, and third plate segments isselected from a group of plate segments of various lengths.
 24. Theplate of claim 21, wherein at least one of said first, second, and thirdplate segments is selected from a group of plate segments of variousconfigurations.
 25. The plate of claim 24, wherein said first, second,and third plate segments are selected from a group including endsegments and intermediary segments.
 26. The plate of claim 25, whereineach of said end segments is configured to connect to one of said endsegments and said intermediary segments, and each of said intermediarysegments is configured to connect to at least one of said end segmentsand said intermediary segments.
 27. The plate of claim 1, furthercomprising at least one bone screw, at least one of said first andsecond plate segments and said bone screw cooperate to lock to saidplate said at least one bone screw inserted in said bone screw receivingholes, respectively.
 28. The plate of claim 1, further comprising atleast one bone screw lock adapted to lock to said plate at least onebone screw inserted in said bone screw receiving holes, respectively.29. The plate of claim 28, wherein said at least one bone screw lock iscoupled to said plate.
 30. The plate of claim 29, wherein said at leastone bone screw lock is removably coupled to said plate.
 31. The plate ofclaim 29, wherein said at least one bone screw lock is adapted to becoupled to said plate prior to the insertion of at least one bone screwinto at least one of said bone screw receiving holes.
 32. The plate ofclaim 28, wherein said at least one bone screw lock is configured tomove from an initial position that permits the insertion of at least onebone screw into at least one of said bone screw receiving holes to afinal position that is adapted to extend over at least a portion of atleast one of the bone screws to retain the bone screw to said plate. 33.The plate of claim 32, wherein said at least one bone screw lock in thefinal position covers at least a portion of at least one of said bonescrew receiving holes.
 34. The plate of claim 32, wherein said at leastone bone screw lock is adapted to be rotated from the initial positionto the final position.
 35. The plate of claim 34, wherein less than afull rotation of said at least one bone screw lock rotates said bonescrew lock from the initial position to the final position.
 36. Theplate of claim 32, wherein at least a portion of said at least one bonescrew lock slides from the initial position to the final position. 37.The plate of claim 36, wherein said at least one bone screw lock slidesover at least a portion of at least one of said bone screw receivingholes.
 38. The plate of claim 37, wherein said at least one bone screwlock slides over at least a portion of at least one bone screw in atleast one of said bone screw receiving holes.
 39. The plate of claim 28,wherein said at least one bone screw lock comprises at least one of ascrew, a rivet, a cap, and a cover.
 40. The plate of claim 28, whereinsaid at least one bone screw lock comprises a head that is at least inpart circular.
 41. The plate of claim 40, wherein said head has at leastone cutout segment.
 42. The plate of claim 28, further comprising atleast one fastener adapted to couple together said first and secondplate segments and wherein said at least one bone screw lock is adaptedto lock to said plate said at least one fastener.
 43. The plate of claim42, wherein said at least one bone screw lock covers at least a portionof at least one of said bone screw receiving holes and at least aportion of said at least one fastener.
 44. The plate of claim 42,wherein said at least one bone screws lock slides over at least aportion of at least one bone screw in at least one of said bone screwreceiving holes and at least a portion of said at least one fastener.45. The plate of claim 1, further comprising at least one fasteneradapted to fasten together said first and second plate segments.
 46. Theplate of claim 45, wherein said fastener is detachably attached to atleast one of said first and second plate segments so as to permitassembly of said first and second plate segments by the surgeon andcomplete uncoupling of said first and second plate segments relative toone another.
 47. The plate of claim 45, wherein said fastener isnon-detachably attached to at least one of said first and second platesegments so as to prevent complete uncoupling of said first and secondplate segments relative to one another.
 48. The plate of claim 45,wherein said fastener has a first position adapted to facilitatemovement of said first and second plate segments in a direction towardone another along the longitudinal axis of said plate and to resistmovement of said first and said second plate segments in a directionaway from one another along the longitudinal axis of said plate.
 49. Theplate of claim 48, wherein said first and second plate segments move inonly a single direction toward one another along the longitudinal axisof said plate when said fastener is in said first position.
 50. Theplate of claim 48, wherein said fastener has a second position adaptedto limit movement of said first and second plate segments relative toone another along the longitudinal axis of said plate.
 51. The plate ofclaim 45, wherein said fastener is configured so as to be able tocompletely restrict movement of said first and second plate segmentsrelative to one another along at least a mid-longitudinal axis of saidplate.
 52. The plate of claim 45, wherein said fastener passes throughat least a portion of said first and second plate segments.
 53. Theplate of claim 45, wherein said fastener is configured to limitseparation of said first and second plate segments relative to oneanother.
 54. The plate of claim 45, wherein said fastener is configuredto be tightened to only one of said at least first and second platesegments so as to permit movement of said first and second platesegments relative to one another.
 55. The plate of claim 45, whereinsaid fastener is a part of a mechanism for moving said first and secondplate segments relative to one another along a mid-longitudinal axis ofsaid plate.
 56. The plate of claim 45, in combination with an instrumentconfigured to cooperatively engage said fastener and at least a portionof at least one of said first and second plate segments so as uponmovement of said fastener with said instrument said first and secondplate segments move relative to one another along a mid-longitudinalaxis of said plate.
 57. The plate of claim 56, wherein said fastener isconfigured to be rotated at least in part by said instrument.
 58. Theplate of claim 45, wherein said fastener is a screw.
 59. The plate ofclaim 45, where said fastener is at least in part threaded.
 60. Theplate of claim 45, wherein said fastener has a head.
 61. The plate ofclaim 60, wherein said fastener has a shaft.
 62. The plate of claim 1,wherein at least one end of said plate is configured to cooperativelyengage a compression tool for movement of at least one vertebral bodytoward another vertebral body during installation of said plate.
 63. Theplate of claim 1, wherein said concave part of said lower surface ofsaid first and second plate segment is configured to conform to theanterior aspect of at least a portion of two cervical vertebral bodies.64. The plate of claim 1, wherein at least a portion of said lowersurface of said first and second plate segment is at least in partconcave transverse to the longitudinal axis of the plate.
 65. The plateof claim 1, wherein at least a portion of said lower surface of saidfirst and second plate segments is roughened to promote the growth ofbone along said lower surface.
 66. The plate of claim 1, wherein atleast a portion of said lower surface of said first and second platesegments comprises a bone ingrowth surface.
 67. The plate of claim 1,wherein at least one of said bone screw receiving holes is configured toform an interference fit with at least a portion of the trailing end ofa properly dimensioned bone screw to be received therein.
 68. The plateof claim 1, wherein at least one of said bone screw receiving holes isconfigured to hold a bone screw in fixed relationship to said plate. 69.The plate of claim 1, wherein at least one of said bone screw receivingholes is configured to allow a bone screw to be in a moveablerelationship to said plate.
 70. The plate of claim 1, wherein at leastone of said bone screw receiving holes is configured to allow a bonescrew to be in a variable angular relationship to said plate.
 71. Theplate of claim 1, in combination with an interbody spinal fusionimplant.
 72. The plate of claim 71, wherein said implant comprises atleast in part bone.
 73. The plate of claim 71, wherein said implant isan allograft interbody bone graft implant.
 74. The plate of claim 71,wherein said implant is an artificial implant.
 75. The plate of claim 1,in combination with a fusion promoting substance.
 76. The plate of claim75, wherein said fusion promoting substance is at least in part otherthan bone.
 77. The plate of claim 75, wherein said fusion promotingsubstance is at least in part bone.
 78. The plate of claim 75, whereinsaid fusion promoting substance is hydroxyapatite.
 79. The plate ofclaim 75, wherein said fusion promoting substance comprises bonemorphogenetic protein.
 80. The plate of claim 75, wherein said fusionpromoting substance comprises genes coding for the production of bone.81. The plate of claim 1, further comprising bone screws for engagingsaid plate to the cervical spine, wherein at least a portion of one ofsaid plate and said bone screws is a bioresorbable material.
 82. Theplate of claim 81, wherein said bioresorbable material is at least inpart bone.
 83. The plate of claim 1, in combination with a substance forinhibiting scar formation.
 84. The plate of claim 1, in combination withan antimicrobial material.
 85. The plate of claim 1, wherein said plateis treated with an antimicrobial material.
 86. The plate of claim 1,further in combination with at least one spinal fixation implant. 87.The plate of claim 1, wherein said plate is electrified for purposes ofstimulating bone growth and contributing to bone fusion.
 88. The plateof claim 28, wherein at least one of said plate and said bone screw lockis electrified for purposes of stimulating bone growth and contributingto bone fusion.
 89. The plate of claim 45, wherein at least one of saidplate and said fastener is electrified for purposes of stimulating bonegrowth and contributing to bone fusion.
 90. The plate of claim 28,further comprising at least one bone screw having a leading end forinsertion into the cervical spine and a head opposite said leading end,said at least one bone screw lock adapted to contact said head.
 91. Theplate of claim 90, wherein said at least one bone screw is configured tobe in fixed relationship to said plate.
 92. The plate of claim 90,wherein said at least one bone screw is configured to be in a moveablerelationship to said plate.
 93. The plate of claim 90, wherein at leastone bone screw is configured to be in a variable angular relationship tosaid plate.
 94. The plate of claim 90, wherein at least one of said bonescrew receiving holes has a reduced dimension proximate said lowersurface of said plate to form a seat, said seat having a substantiallyplanar surface adapted to contact a lower surface of one of said bonescrews.
 95. A method for stabilizing at least two adjacent vertebralbodies in the cervical human spine, comprising the steps of: providing aplate of appropriate length adapted to overlap at least a portion of twoadjacent cervical vertebral bodies anteriorly, said plate having atleast a first plate segment adapted to be attached to one of theadjacent vertebral bodies to be fused and a second plate segment adaptedto be attached to another one of the adjacent vertebral bodies to befused, the first and second plate segments being in moveablerelationship to one another along a longitudinal axis of the plate, thefirst and second plate segments being configured to couple together incooperative relationship; inserting at least two bone screws through thefirst plate segment of the plate and into one of the vertebral bodiesadjacent the disc space to be fused; inserting at least two bone screwsthrough the second plate segment and into the other of the vertebralbodies adjacent the disc space to be fused; and permitting movement ofthe first and second plate segments attached to the adjacent vertebralbodies relative to one another in a direction toward one another alongthe longitudinal axis of the plate and resisting movement of the firstand second plate segments in a direction away from one another along thelongitudinal axis of the plate.
 96. The method of claim 95, wherein thepermitting step includes the step of permitting movement of the firstand second plate segments in only a single direction toward one another.97. The method of claim 95, wherein the permitting step includes thestep of allowing but not causing the movement of the adjacent vertebralbodies by movement of the first and second plate segments of the plate.98. The method of claim 97, wherein the permitting step includes thefirst and second plate segments being free to move toward one another.99. The method of claim 95, wherein the permitting step includes thestep of allowing movement of the first and second plate segments of theplate in response to movement of the adjacent vertebral bodies.
 100. Themethod of claim 95, wherein the permitting step includes the sub-step oflimiting the movement of the first and second plate segments relative toone another to sequential increments along the longitudinal axis of theplate.
 101. The method of claim 95, wherein the permitting step includesthe step of causing movement of the adjacent vertebral bodies by movingthe first and second plate segments relative to one another.
 102. Themethod of claim 101, wherein the step of causing movement of theadjacent vertebral bodies includes the step of generating a compressiveload across the disc space between the adjacent vertebral bodies. 103.The method of claim 102, wherein the permitting step includes the firstand second plate segments being free to move toward one another. 104.The method of claim 101, wherein the step of causing movement of theadjacent vertebral bodies includes the step of storing a compressiveload across the disc space between the adjacent vertebral bodies. 105.The method of claim 104, wherein the permitting step includes the firstand second plate segments being in fixed relationship to one another.106. The method of claim 95, further comprising the step of providing afastener to fasten together the first and second plate segments. 107.The method of claim 106, further comprising the steps of providing aninstrument configured to cooperatively engage the fastener and at leasta portion of at least one of the first and second plate segments, andutilizing the instrument to move the fastener and the first and secondplate segments relative to one another along a mid-longitudinal axis ofthe plate.
 108. The method of claim 107, wherein the utilizing stepincludes the sub-step of rotating the fastener at least in part with theinstrument.
 109. The method of claim 106, further comprising the step oftightening the fastener from a first position to a second position toresist movement of the first and second plate segments relative to eachother in at least one direction.
 110. The method of claim 109, whereinthe tightening step includes resisting movement of the first and secondplate segments relative to one another when the fastener is in thesecond position.
 111. The method of claim 109, wherein the tighteningstep includes permitting movement of the first and second plate segmentsrelative to one another when the fastener is in the second position.112. The method of claim 111, wherein the wherein the tightening stepincludes limiting the movement of the first and second plate segmentsrelative to one another to one direction along the longitudinal axis ofthe plate.
 113. The method of claim 111, wherein the tightening stepincludes limiting the movement of the first and second plate segmentsrelative to one another to sequential increments along the longitudinalaxis of the plate.
 114. The method of claim 109, wherein the tighteningstep includes tightening the fastener to cause the fastener to tightento the first plate segment while permitting movement of the first andsecond plate segments relative to one another.
 115. The method of claim95, further comprising the step of adjusting the overall length of theplate by moving the first and second plate segments relative to eachother.
 116. The method of claim 95, wherein the providing step includesselecting at least one of the first and second plate segments from agroup of plate segments of various lengths.
 117. The method of claim 95,wherein the providing step includes selecting at least one of the firstand second plate segments from a group of plate segments of variousconfigurations.
 118. The method of claim 95, wherein the providing stepincludes providing a plate having at least a third plate segment. 119.The method of claim 118, wherein the providing step includes selectingat least one of the first, second, and third plate segments from a groupof plate segments of various lengths.
 120. The method of claim 118,wherein the providing step includes selecting at least one of the first,second, and third plate segments from a plurality of plate segments ofvarious configurations.
 121. The method of claim 95, further comprisingthe step of locking at least one of the bone screws to the plate. 122.The method of claim 121, wherein the permitting step occurs prior to thelocking step.
 123. The method of claim 95, wherein the permitting stepincludes the sub-step of moving the first and second plate segmentsrelative to one another after the step of inserting the bone screws.124. The method of claim 95, wherein the permitting step includes thesub-step of moving the first and second plate segments relative to oneanother before the step of inserting the bone screws.
 125. The method ofclaim 95, wherein the permitting step includes the sub-step of applyinga compressive load to the adjacent vertebral bodies.
 126. The method ofclaim 95, wherein the permitting step includes moving the first andsecond plate segments from a first position to a second position. 127.The method of claim 95, further comprising the step of combining theplate with an interbody spinal fusion implant.
 128. The method of claim127, wherein the implant comprises at least in part bone.
 129. Themethod of claim 127, wherein the implant is an allograft interbody bonegraft implant.
 130. The method of claim 127, wherein the implant is anartificial implant.
 131. The method of claim 95, further comprising thestep of combining the plate with a fusion promoting substance.
 132. Themethod of claim 131, wherein the fusion promoting substance is at leastin part other than bone.
 133. The method of claim 131, wherein thefusion promoting substance is at least in part bone.
 134. The method ofclaim 131, wherein the fusion promoting substance is hydroxyapatite.135. The method of claim 131, wherein the fusion promoting substancecomprises bone morphogenetic protein.
 136. The method of claim 131,wherein the fusion promoting substance comprises genes coding for theproduction of bone.
 137. The method of claim 95, wherein the providingstep further comprises the step of providing bone screws for engagingthe plate to the cervical spine, wherein at least a portion of one ofthe plate and the bone screws is a bioresorbable material.
 138. Themethod of claim 137, wherein the bioresorbable material is at least inpart bone.
 139. The method of claim 95, further comprising the step ofcombining the plate with a substance for inhibiting scar formation. 140.The method of claim 95, further comprising the step of combining theplate with an antimicrobial material.
 141. The method of claim 95,further comprising the step of treating the plate with an antimicrobialmaterial.
 142. The method of claim 95, further comprising the step ofelectrifying at least one of the plate and the bone screws for purposesof stimulating bone growth and contributing to bone fusion.
 143. Themethod of claim 106, further comprising the step of electrifying atleast one of the plate, the fastener, and the bone screws for purposesof stimulating bone growth and contributing to bone fusion.